There are a number of different devices which are used for rapid, accurate spectrographic analysis of the reflectivity, transmissivity or transflectance of the samples. One such device is disclosed in U.S. Pat. No. 4,540,282 to Landa. This patent discloses that a device which enables immediate and rapid analysis of a number of different products. This type of device can measure three generalized types of information; the chemical constituents of a sample, the physical constituents of a sample and a quality of the sample. The chemical constituents of a product includes such things as the octane number in gasoline or the amount of aromatics in gasoline. In another environment, such items such as the amount of protein, starch, oil and other characteristics of the food may be measured. Yet another environment such blood constituents such as glucose or cholesterol can be measured using such a device. In the area of pharmaceuticals, the drug composition of a sample can be determined and such features such as the active zones of drugs can be measured. In the tobacco industry, the chemical characteristics such as nicotine, tar and methol can be measured using such device.
The second broad type of characteristics which can be measured using such a device are called physical parameters. Such physical parameters include physical characteristics such as the viscosity of liquids. In addition, the characteristics such as molecular weight or the multi-layer thickness of various coatings can be measured.
The third major area which can be measured using the device described in the Landa patent are "quality parameters" such as the degree of bake, for example, it may be necessary to determine when a cookie is properly cooked. One can use the spectral response from the cookie in the process of it being cooked to determine when to stop cooking.
Another area in which quality parameters can be measured involves, for example, adhesive strength. Another example of how the device disclosed in the Landa patent may be used in determining the taste of beers or wines. Since each of these products have a spectral signature, it is possible to determine the quality of wine by comparing the spectral signature of that wine with a known product or standard. For example, once the quality of a particular wine is known, it may be possible to take a spectral signature of that wine and determine what spectral characteristic or signature other wines must have in order to similarly have a good taste. Thereafter, other wines need not be taste-tested in order to determine that they are good wines. A spectral analysis need only be done and a signature be taken in order to determine such a characteristic.
Another example is that once the quality of a particular cheese is known, it may be possible to take a spectral signature of that cheese and determine what spectrographic characteristic or signature other cheeses may have in order to have a similarly good taste. Thus, other cheeses need not be taste-tested in order to determine that they are good cheeses. Similar to the wines, the spectral analysis need only be done on a signature viewing be taken in order to determine such characteristic.
There are basically three modes of introducing and detecting light from a sample. The first way is through reflectance. In the reflectance mode, the light is introduced into a sample by a probe. The light is then reflected back to the probe and the probe relays this information to the instrument which analyzes the light returned. Generally, this type of instrument will have a bi-directional fiber arrangement which enables light to move in two directions through the probe. With a reflective type of sample cell, the surface of this cell must be completely cleared of material between samples. With a reflective type, the infrared energy used to analyze the sample, penetrates approximately 5-10 micrometers into the material before the infrared energy is reflected or absorbed thus even a small amount of material remaining on the optical surface causes error in the measurement.
A second mode of operation is transmittance. In this mode, a first probe introduces light to a sample and a second probe will receive that light which has been transmitted through the sample. In this mode, two probes are necessary. One probe with this mode is that the sample could accumulate on the two probes, preventing fresh sample from passing between the probes and results in inaccurate reading.
The third mode of operation is transflectance mode. This mode is similar to the reflectance mode in that a bi-directional fiber is generally used which transmits and receives light from the sample. In this mode, light is introduced to the sample. Light which is reflected from the sample is returned through the probe and transmitted back to the instrument for analysis. The light which transmits to the sample is reflected by a mirror back to the sample and again through the probe and onto the instrument for analysis.
In order to obtain data for analysis, a probe may be inserted into a pipe to detect the constituents of a particular liquid product. If the probe is an optical rod surrounded by a sleeve, there can be a serious problem with the introduction of liquid between the rod and the sleeve. This occurs if there are problems with the seal which are tended to prevent liquid from flowing between the rod and sleeve. If such a problem occurs, the entire probe may be needed to be replaced. The reason that this is a serious problem in that each probe has particular characteristics. Therefore, by replacing one probe with another, the spectral signature which results may be altered as a function of the probe rather than a function of the material being analyzed.
Other probes in the art are made of the unitary structure. That is, an optical bundle or the like may be surrounded by an epoxy to the sleeve. Thus, any failure in the optical bundle requires replacement of the entire probe. Since each probe has a distinct personality, the reliability of data is decreased. The above-described unitary construction as an additional problem in that upon connecting the probe to the pipe or any other body a torque is necessarily required. If the probe is of unitary construction, any torque to the sleeve has a corresponding torque to the optical bundle. Such a torque can damage the probe, thus causing additional delays and costs.
Furthermore, U.S. Pat. No. 5,044,755 issued Sep. 3, 1991, to Landa discloses an optical rod or other device for propagating light, an optical barrel which in part surrounds the optical rod and the sleeve which is permitted to attach the probe to the source of light such as a fiber-optical bundle. This probe may be fitted with a bi-directional focusing adapter and a reflective tip.